Uiview 为什么我的UIScrollView没有出现？

我正在尝试对一个包含UIScrollView的UIView进行子类化。这是我正在使用的代码：

UIViewSubclass.h

 @property (nonatomic, retain) UIScrollView *scroll;

UIViewSubclass.m

 @synthesize itemScrollView;

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {

    [self setUpScrollViewWithIdentifier:@"id"];
}
return self;
}

-(void)setUpScrollViewWithIdentifier:(NSString*)scrollViewID {

NSLog(@"Setting up Scroll View with the id of: %@",scrollViewID); //This is working

scroll = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 0, 320, 90)];

//Subview of the scroll view
UIView *test = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 50, 50)];
test.backgroundColor = [UIColor blueColor];
[scroll addSubview:test];

[self addSubview:scroll]; // Adds the scrollview to the UIView
 NSLog(@"Subviews: %@",self.subviews);
}

ViewController.h

  #import "UIViewSubclass.h"

  IBOutlet UIViewSubclass *menuView;

视图控制器.m

- (void)viewDidLoad
 {
menuView = [[UIViewSubclass alloc]init];
[super viewDidLoad];
// Do any additional setup after loading the view.
}

我还在故事板中链接了视图，并将视图的类设置为UIViewSubclass，但由于某些原因，滚动视图不会出现。但当我查看此NSLog时：

 NSLog(@"Subviews: %@",self.subviews);

它在调试器中为我提供了以下信息：

Subviews: (
"<UIScrollView: 0x1d5a20e0; frame = (0 0; 320 90); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x1d5a2420>; layer = <CALayer: 0x1d5a1c60>; contentOffset: {0, 0}>"
 )

子视图：(
""
)

那么我做错了什么

scroll.contentSize = fooSize;

可能是你错过了什么